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Hydrogen-Bonded Architectures and Field-Induced Polarization Switching in Bridged Bis(benzimidazole) Crystals
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2018-12-05 00:00:00 , DOI: 10.1021/acs.cgd.8b01436
Sachio Horiuchi 1 , Shoji Ishibashi 2 , Satoshi Inada 3 , Shigenobu Aoyagi 3
Affiliation  

The imidazole ring is chemically stable and forms an excellent building block for compounds that show externally switchable polarization in their crystalline states. We examined the structural properties of nine bridged bis(benzimidazole)s, of which seven were new compounds, in an attempt to identify substances with highly polarizable dielectric properties arising from the multistability of their polar supramolecular architectures. Selected bridging o-phenylene, thien-2,5-diyl, or 1H-imidazole-4,5-diyl units improved the thermal robustness as expected. Solution evaporation or vacuum sublimation of the bridged bis(benzimidazole)s afforded single crystals, with or without solvent molecules, in which the molecules were hydrogen bonded to form either extended ribbons or cyclic oligomeric structures. 2,2′-(1,2-Phenylene)bis-1H-benzimidazole (BI2P) formed ladder-like ribbons that exist as low- or high-dipole configurations depending on the parallel or antiparallel orientation of the NH hydrogen atoms between the two benzimidazole rings. These two configurations were nearly degenerate in stability, permitting them to be electrically switched, as evidenced by their double (PE) hysteresis curves. The switching process was ascribed to an order–disorder-type paraelectric-to-ferroelectric phase transition rather than to an antiferroelectric-to-ferroelectric phase transition. BI2P is also unique as a paraelectric crystal in which the ferroelectric state is field induced but is unexpectedly inaccessible by exclusively thermal stimulation.

中文翻译:

桥联双(苯并咪唑)晶体中的氢键结构和场致极化转换

咪唑环在化学上是稳定的,并形成了在晶体状态下可外部转换极化的化合物的优异结构单元。我们研究了九种桥联双(苯并咪唑)的结构特性,其中七种是新化合物,试图鉴定出由于其极性超分子结构的多重稳定性而具有高度可极化介电特性的物质。选定的邻-亚苯基,thien-2,5-二基或1 H桥接-咪唑-4,5-二基单元提高了热稳定性,符合预期。溶液蒸发或桥联双(苯并咪唑)的真空升华提供具有或不具有溶剂分子的单晶,其中分子与氢键结合以形成延伸的带或环状低聚物结构。2,2'-(1,2,亚苯基)双-1H-苯并咪唑(BI2P)形成梯状带,根据两个氢原子之间的NH氢原子的平行或反平行方向以低或高偶极构型存在苯并咪唑环。这两种配置的稳定性几乎退化,因此可以电气开关,这由它们的双倍(PE)磁滞曲线。开关过程归因于有序-无序型顺电-铁电相变,而不是反铁电-铁电相变。BI2P作为顺电晶体也是独特的,在该顺电晶体中,铁电态是场感应的,但是出乎意料的是,仅通过热刺激无法进入。
更新日期:2018-12-05
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